This invention relates to a spring for biasing a radially slidable vane in a rotary fluid power converter.
Fluid power converters such as vane-type air motors have a rotor with vanes free to slide in radial vane slots. The rotor is eccentrically mounted within an enclosed cylinder which allows the vanes to radially project from the rotor during the cycle of rotation. Fluid pressure acts on one side of the projecting vanes to create torque on the rotor shaft. The vanes are biased radially outward to seal against the cylinder. A good seal is especially important during start-up and for operation at low rotational speeds.
For vanes that are short in both radial height and axial length but have considerable radial travel, a double torsion spring having a conventional straight configuration is often used as the biasing mechanism. The conventional spring results in many spring failures and leakage around the vanes. A straight wire connects the two coils of the double torsion spring and supports the base of the vane. The vane base rubs against the connecting wire causing wear and eventually failure of the spring. A straight arm member extends from each coil and has rounded tips which abut against the bottom of the vane slot. As the motor rotates and the vanes move in and out of the slots, the springs deflect and the arm tips slide on the bottom of the vane slot. This sliding results in wear and eventual failure of the spring. At maximum vane extension, the short vane height results in a small portion of the vane remaining within the vane slot to support the pressure loaded cantilevered portion of the vane outside of the vane slot. Without adequate support in the slot, the vanes are subject to misalignment and increased wear and leakage around the vane.
An air motor with a broken spring or worn vanes does not operate efficiently and must be disassembled to replace the broken or worn parts. These repairs cause costly down time for a mechanism powered by an air motor.
The present invention is directed to various improvements in vane springs to overcome these problems.